Heretofore, customers using ATMs of this type have been assigned, for personal identification, character strings for authentication that are composed of a predetermined number of digits (hereinafter referred to as “PIN numbers”).
At the time of a withdrawal, an ATM prompts a customer to press operation surfaces of operation keys of an entry section in sequence to enter a PIN number, by touching the fingertips of their hand against the operation surfaces of the operation keys. When the customer has been authenticated in accordance with the entered PIN number, the customer withdraws cash.
However, if a PIN number used for the authentication of a customer is illegitimately acquired by a third party, the third party may misuse the PIN number for crimes such as posing as the customer and dishonestly taking out cash.
Recently, a variety of techniques have been identified by which, when a customer is using an ATM and entering their PIN number in order to withdraw cash, a third party is surreptitiously trying to illegitimately acquire the customer's PIN number.
Previously, therefore, to counter these techniques for the illegitimate acquisition of PIN numbers, some ATMs of this type have been provided with structures that may prevent the illegitimate acquisition of PIN numbers.
The techniques for illegitimate acquisition of PIN numbers that have so far been identified include, for example, attaching a fake entry section so as to cover the entry section of an ATM, the fake entry section being formed with a similar external appearance and arrangement of operation keys to the ATM's entry section. Thus, a customer is made to think that the fake entry section is the ATM's entry section and operate the fake entry section, and the PIN number may be illegitimately acquired in this manner.
An ATM that is structured to counter this technique for the illegitimate acquisition of PIN numbers focuses on the fact of the entry section being covered over by the fake entry section. Before a PIN number is entered at the time of a withdrawal, this ATM illuminates a predetermined operation key of the entry section and prompts the customer to press the illuminated operation key.
That is, the ATM prompts the customer to identify the illuminated operation key and, if the entry section is not covered by a fake entry section, the illuminated operation key can be pressed in accordance with this instruction.
However, if the entry section of the ATM is covered over by a fake entry section, the customer cannot identify the illuminated operation key and cannot press the illuminated operation key in accordance with the instruction.
Hence, the ATM with this structure prompts the customer to enter their PIN number at the time of a withdrawal only when the customer has pressed the illuminated operation key. If the operation key is not pressed, the ATM instructs the customer not to enter their PIN number.
An ATM with this structure prevents a customer's PIN number from being illegitimately acquired even if a fake entry section has been attached so as to cover the entry section (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2011-100383 (page 6, page 7 and FIG. 6)).
Meanwhile, in recent years it has been reported, by a research team led by Keaton Mowery at the University of California in the USA, that when the fingertips of a hand touch the operation surfaces of operation keys, temperatures of the operation surfaces are changed by the touch of the fingertips. Therefore, when a customer has pressed plural operation keys and entered their PIN number, if the temperatures of the operation surfaces of the plural operation keys are sensed using thermography, as illustrated in FIG. 23, the operation keys that have been pressed and the order of pressing operations may be analyzed from the sensing results, so the PIN number may be identified (Keaton Mowery, Sarah Meiklejohn, Stefan Savage; “Heat of the Moment: Characterizing the Efficacy of Thermal Camera-Based Attacks”: Internet URL: http://static.usenix.org/events/woot11/tech/final_files/Mowery.pdf).
That is, using thermography to sense temperatures of the operation surfaces of plural operation keys at an ATM when the plural operation keys have been pressed by a customer to enter a PIN number has been reported as being a feasible new technique for a third party to illegitimately acquire the customer's PIN number.